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Thread: Simms Watt 100w Head

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    Simms Watt 100w Head

    Hi,

    I last used my Simms Watt 100w Head about 20 years ago. The best is around 48 years old.
    I'm now planning to start it up, and fix it I guess...

    Do you have any advises on how to start it up after so many years out of business?

    I first need to get a mains cable, since I lost it, somewhere in time.

    Here's some pics of the amp.

    https://s3-ap-southeast-1.amazonaws....mswatt/p0.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p1.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p2.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p3.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p4.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p5.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p6.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p7.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p8.jpeg
    https://s3-ap-southeast-1.amazonaws....mswatt/p9.jpeg
    https://s3-ap-southeast-1.amazonaws....swatt/p10.jpeg
    https://s3-ap-southeast-1.amazonaws....swatt/p11.jpeg

    I don't have real electronics experience. I can replace simple components and trace them down on the schematics. Last year I managed to bring back to life my old Marshall Valvestate, I just ended up replacing all the main caps of the amp. I hope this doesn't get much more complex though.

    Any hints or suggestions are welcome.

    Cheers.

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  2. #2
    Don't forget the joker g1's Avatar
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    You should build a light bulb limiter to plug it into when you first start it up. It will prevent and serious damage in case any components have failed.

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

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    Bent Member Chuck H's Avatar
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    Well... What I see is that somewhere along the line someone (probably on more than one occasion) kludged that amp with an odd assortment of filter caps (one of which is axial instead of radial) and added a series resistor to the B+ string after the standby switch putting exposed high voltage nodes within reach of the user from outside of the amp. All I can say is that this is a very bad thing that can result in death if such an accident were to happen. Soooooo...

    I would undo that stuff for certain. On the other hand, if the amp worked for you the last time you used it, you have had no trouble and liked the amp as it was then there is the probability that removing the HV rail resistor will change the response of the amp a little. But at the very least that resistor should be mounted on a terminal strip INSIDE the chassis and that axial lead HV capacitor should be replaced with a radial capacitor.

    But I suspect all the electrolytic caps will need to be replaced due to age and disuse. Twenty idle years will kill most electrolytic caps. As g1 said (and if you're comfortable with the dangers I noted) you can bring the amp up on a limiter for a few hours and the caps may survive. Though they may not perform well and you would experience extra noise, hum and odd harmonic overtones.

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    "...less ear-friendly but handy for jazz." Leo_Gnardo

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    G1 and Chuck H. thanks for the quick responses.

    When I worked on the Valvestate I paid extra attention to discharging big caps and so. And this one looks much more scary. I'll definitely check the light bulb limiter stuff.

    Yeah those resistors were mounted by a "professional" many years ago, the amp worked fine after that. But I'll follow your advice and at least move them to the inside. If I knew what was the original setup of those resistors I would try to get them close to those.

    Unfortunately I don't have complete schematics. I guess all I have is this: https://drtube.com/schematics/simms/100w-amp.gif

    Regarding that axial lead HV capacitor. Could you please point out which one you mean, on which pic?

    Yep, I understand the caps aging. Lets see if I can carefully bring it up and see what comes out of the amp.

    Currently I can only try it out with a cabinet that has a single 12" speaker at 8.0 hm. Do you think it would be an issue connecting it to that once I can start it?

    PS: I tried to give thumbs up to both and it didn't work as I expected. But again, thanks a lot for your comments.

    UPDATE: Actually, I've seen now a few more pictures of that amp, and all seem to have the resistor on the outside:
    http://i76.photobucket.com/albums/j1...06/chassis.jpg
    http://www.tdpri.com/proxy.php?image...f0591ef83ff038

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    Last edited by josegrad; 09-30-2018 at 10:54 AM.

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    picture 9 it's the blue one. The negative lead is sticking up outside of the chassis and a wire goes back into the chassis to connect to ground inside the amp

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by josegrad View Post
    UPDATE: Actually, I've seen now a few more pictures of that amp, and all seem to have the resistor on the outside:
    Well looky there! Ok... Not how I would have done it. A bit dangerous and you sure couldn't design the amp like that today. But I should have looked for myself before critiquing. The grommet sort of hinted that it might be a stock installation, but I thought "No way anyone chose to sell the amp new like that." I was wrong.

    NBD on mounting the axial cap with the ground lead sticking out of the chassis. There's no HV on that lead. I've done sort of the opposite mounting radial caps on boards made for axial caps. The amp doesn't know the difference

    Good luck with the light bulb limiter. I've done exactly the same thing. I knew a guy that had two NOS amps still in the factory cardboard box (25 years old). I warned him about the filter caps and their age but he wasn't sure I knew what I was talking about because, you know, these are brand new and never used! So he plugged one in and it smoked and burped electrolyte all over the innards in about five minutes. So we brought the other up with a light bulb limiter for about four hours in idle with the standby in play mode. That amp did "work". But it was noisy and had the odd harmonic overtones I mentioned. I ended up replacing the electrolytic caps in both amps before it was over.

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    Hi there,

    I have a question about the schematic I'm following.
    I think I should have almost everything with the top part of this:

    Click image for larger version. 

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    And this:

    Click image for larger version. 

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    But I'm not sure which part is that area on the left that says "3x1AT". Where is that located?

    ----

    On the other hand I just got a Bulgin connector from the UK.

    In the attached image you can see how the power connector is connected inside the amp. With a Red, Green and Black cable.
    Then there's the cable I'll use with Blue, Brown and Yellow/Green.

    If I'm not mistaken the cables should end up like in the table below.
    I'll appreciate any corrections obviously.

    AMP NEW CABLE FUNCTION
    Red Brown Live wire
    Green Yellow/Green Grounding
    Black Blue Neutral

    Click image for larger version. 

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    After that I'll start building the light bulb limiter and see what happens when I turn it on.

    I know this is not an electricians course, but any comments on my connection plans will we appreciated. Just in case.

    Thanks in advance.

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    Quote Originally Posted by josegrad View Post
    But I'm not sure which part is that area on the left that says "3x1AT". Where is that located?
    It looks like a mod to add three 1A T fuses to the standby switch area. I think the fuse marked with an 'X' is to go in series with the bias winding where it's marked with a second 'X'

    The wire colour table is correct.

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    Thanks Dave.

    Connection done.

    I'm now investigating how big of a bulb I need to use for the light bulb limiter with this amp.
    I guess I'll need pretty big bulb. Now sure if I can still get big enough to buy.

    Cheers.

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  10. #10
    Bent Member Chuck H's Avatar
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    You can probably still get 200W or 250W incandescent outdoor spots at any hardware store.?. It doesn't need to be "light bulb" shaped.

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    Too big of a bulb defeats the purpose. It will limit too late.
    I've seen people use a rough rule of thumb that the bulb should be the same wattage as the amps output power. That being said, I don't think you need to use less than a 100W bulb for low power amps.
    The bulb is only used when getting the idle conditions correct. Then you get off the bulb to do any signal or power output testing.

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

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    Bent Member Chuck H's Avatar
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    I don't know why, but when I read that Jose thought the limiter had to be matched to THIS amp I saw the title "Simms 200W head" in my mind.

    The typical 100W bulb would be fine.

    You can still get incandescent hundys in specialty bulbs. You may need to order them on line. I still have a couple of plain ol "light bulbs" in my stash. But I'm sure I'd come up with something if I didn't.

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    "...less ear-friendly but handy for jazz." Leo_Gnardo

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    "A shot gun delivers a force that exceeds the operational range of most systems, such as pumpkins." Antigua

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    Ha,

    Did I mention I'm in Finland? I can find trees and lakes of any size.

    And also these bulbs I can get easily:

    Click image for larger version. 

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    But 100W old style bulbs are harder to get. Hmm, I bet the Russians have

    Cheers.

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    Quote Originally Posted by josegrad View Post
    Ha,

    Did I mention I'm in Finland? I can find trees and lakes of any size.

    And also these bulbs I can get easily:

    Click image for larger version. 

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    But 100W old style bulbs are harder to get. Hmm, I bet the Russians have

    Cheers.
    Nothing wrong with halogen bulbs, as shown in your picture. They are incandescent lamps and work just as fine as the old ones as limiters.

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by Helmholtz View Post
    Nothing wrong with halogen bulbs, as shown in your picture. They are incandescent lamps and work just as fine as the old ones as limiters.
    And typically last longer AND make a nicer spectrum of light If it mattered.

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    "...less ear-friendly but handy for jazz." Leo_Gnardo

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    "Now get off my lawn with your silicooties and boom-chucka speakers and computers masquerading as amplifiers" Justin Thomas

    "A shot gun delivers a force that exceeds the operational range of most systems, such as pumpkins." Antigua

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    The three big electrolytic capacitors show up in the images as 100uF, no idea the blue one, and 16uF.

    Click image for larger version. 

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    I'm not 100% sure where those are in the schematics.
    Any hints?

    Click image for larger version. 

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    Click image for larger version. 

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    Thanks.

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  17. #17
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    I've labelled your pic with the node letter and the capacitance value used in the schematic:

    Click image for larger version. 

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    Quote Originally Posted by nickb View Post
    I've labelled your pic with the node letter and the capacitance value used in the schematic
    Thanks nickb, I'll start looking for replacements.

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    Light bulb limiter ready. Capacitors changed. New fuses in place.

    I'm quite close to start the amp again. With a speaker and a single hand of course.

    But it is hard to place it somewhere where nothing touches the bench I have.
    I guess there's no danger in placing it on the transformers like in the image below.

    Click image for larger version. 

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    Cheers.

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    No danger. Make sure the tubes don't burn/melt anything, and make sure it's secure enough that if you scare yourself, you don't end up with it sitting on your lap, or broken on the floor.

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    Quote Originally Posted by The Dude View Post
    But, I did learn something. There are protons, neutrons, electrons, ............ and morons.

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    Quote Originally Posted by g1 View Post
    No danger. Make sure the tubes don't burn/melt anything, and make sure it's secure enough that if you scare yourself, you don't end up with it sitting on your lap, or broken on the floor.
    Thanks g1. Yeah maybe I'll put it a bit higher on the bench so there's more space below the tubes.
    I'll get the crocodile clips in place to discharge the caps before touching anything in between when needed.

    It is close by the door, in case of danger I'll open the door and throw it away

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    Old Timer J M Fahey's Avatar
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    Quote Originally Posted by josegrad View Post
    Ha,

    Did I mention I'm in Finland? I can find trees and lakes of any size.

    And also these bulbs I can get easily:

    Click image for larger version. 

Name:	bubls.jpeg 
Views:	30 
Size:	79.0 KB 
ID:	50727

    But 100W old style bulbs are harder to get. Hmm, I bet the Russians have

    Cheers.
    I bet a bulb which irradiates 70% of energy into the room as infrared waves is an asset, not a liability, if we are talking sub-zero Countries.

    Which of course includes Finland

    I always suggest using 100/150/250W halogen "stick" lamps which are widely available anywhere without special ordering.


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    Right.

    I have now verified that the light bulb limiter operates properly by using another amp.

    When I use it with this amp and I switch ON the mains, the bulb stays on all the time.
    I have not yet switched on the stand by one.
    Only the one on the right switched.

    Click image for larger version. 

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    Is it as bad as it looks, or should I switch both ON?

    Cheers.

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    Actually. When only the mains are ON the bulb stays light, but I can still look at it. If I light the bulb alone you cannot look at it.

    I turned the light off and I can see the the 4 big valves are lighting up a bit.

    I guess I could leave it on for a while, and then turn ON the other switch.

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  25. #25
    Bent Member Chuck H's Avatar
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    If the bulb is lighting brightly with the standby switch in the silent position you may have a bad rectifier or main filter cap. If you lift the PT secondary leads from the rectifier and the bulb lights brightly you have a shorted PT.

    Don't flip the standby switch into play mode yet and don't remove the bulb limiter from the test circumstances yet.

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    Old Timer J M Fahey's Avatar
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    Agree and add: please try amp as-is, same bulb limiter, etc. , but pulling all tubes from it, so we remove filament load, which is significative.

    What happens with lightbulb brightness?
    Stays the same?
    We have less? (itīs somewhat darker).

    The point I want to check is that since tube amps in general are power guzzlers even at idle, and that Simms Watts may be even more so, I want to know whether that idle lightbulb brightness comes from a lossy transformer or simply we "should" be using a somewhat higher wattage bulb.

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    I removed all the valves from the amp, 8 in total.

    When switching ON the mains the light bulb didn't light up at all. To my surprise the front bulb of the amp did light up, but only for a couple of times, then when I tried again it didn't light up anymore. The bulb limiter didn't light up at all as I mentioned.

    @chuck, does PT stands for Power Transformer? Sorry, I'm not a pro so I can't get all the acronyms.

    Thanks for the hints.

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    Bent Member Chuck H's Avatar
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    Quote Originally Posted by josegrad View Post
    I removed all the valves from the amp, 8 in total.

    When switching ON the mains the light bulb didn't light up at all. To my surprise the front bulb of the amp did light up, but only for a couple of times, then when I tried again it didn't light up anymore. The bulb limiter didn't light up at all as I mentioned.

    @chuck, does PT stands for Power Transformer? Sorry, I'm not a pro so I can't get all the acronyms.

    Thanks for the hints.
    Yes, PT is an acronym for power transformer.

    It's possible that the pilot lamp has a bad or dirty connection? I don't see the pilot lamp in the schematics.?.

    That the bulb didn't light at all is actually impossible if even the pilot lamp was on. But it could be that when the pilot lamp was on that the limiter bulb was so dim that you couldn't tell it was lit at all.

    I'm confused by the results. Just to confirm, with the tubes in and the standby switch in the silent position the limiter bulb glows brightly, and with the tubes out and the standby still in the silent position the limiter bulb doesn't glow at all.

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  29. #29
    Old Timer J M Fahey's Avatar
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    I'm confused by the results. Just to confirm, with the tubes in and the standby switch in the silent position the limiter bulb glows brightly,
    Define "brightly" ... and josegrad never said that, you just assume he did.

    No, not brightly at all, we are having a language or interpretation barrier here.

    My take, and that is why I asked for tubes removal to minimize load, is that josegrad just mentions "the filament being visible" , not the same:

    When I use it with this amp and I switch ON the mains, the bulb stays on all the time.
    NOT "full on bright" (as if connected straight to mains in a desk lamp) which is a very different thing.
    In fact josegrad mentions *two* brightness levels:

    Actually. When only the mains are ON the bulb stays light, but I can still look at it.
    In my book that means "attenuated" brightness, meaning amp which is in series with bulb is NOT a short.
    If I light the bulb alone you cannot look at it.
    *
    I understand that as full brightness, bulb straight into mains, no amp involved.
    In fact I asked for and got a *third* brightness level :
    I removed all the valves from the amp, 8 in total.
    When switching ON the mains the light bulb didn't light up at all.
    which means idle current, with no tube filament load, is not enough to heat bulb filament enough to be visible in daylight.
    I *guess* it will be dark red if seen in the dark.

    In a nutshell, so far I guess PT, main rectifiers and filter caps are fine.

    josegrad should (carefully, DEADLY voltage there) measure voltage with Standby OFF, just before the switch.
    Would not be surprised to find some 400 V or more there.
    Which would confirm my earliest assumption.

    As of the intermittent pilot light, no big deal, tarnished/rusty/dirty contacts are common after 48 years.

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    Bent Member Chuck H's Avatar
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    You're probably right Juan. I interpreted his description "I can still look at it" not so much as attenuated, but barely attenuated. Otherwise why mention it like that.?. So could be a bad assumption on my part. My concern was a heavy current load with no high voltage on the tubes. But with eight tubes in the amp I suppose the filament load could get the limiter bulb pretty bright.

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    The next pictures are with all valves on again.

    First with the bulb connected directly to the wall. That's how it looks normally, you can look at it just for a moment, but not pleasant at all. Just a normal bulb on.

    Click image for larger version. 

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    Next a picture of the bulb with the amp connected, just mains ON. You can look at the bulb quite ok, no sunglases needed.

    Click image for larger version. 

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    Not sure how useful the pic is because the amps are so different. But anyway here's another pic of the limiter when connected to a working 100w Marshall Valvestate.

    Click image for larger version. 

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    -----

    Regarding the amp bulb yeah I cannot see it in the schematics either. I did more tests around it.

    When the amp was with all the valves on it didn't light up at first. With a wooden stick I hit here and there around the area where the diodes and bias cap are, and then it lighted up, not full light but clearly visible on. Sometimes it would go off and then on after hitting again.

    I took the valves out again and the bulb in the amp lights up normally, I can hit around with the stick and it just stays on.

    At least I guess I should take that part out and re-solder it again.

    ------

    One thing I've done every time I've switched it on is checking the bias capacitor, to see if there was any voltage stored in it. I haven't been able to get any readings from it so far. That cap is among the ones I have replaced.

    ------

    josegrad should (carefully, DEADLY voltage there) measure voltage with Standby OFF, just before the switch.
    I'm sure I can do it safely but didn't measure that. I'm not sure where to place the probes. You mean just before the second switch? I know one of the cables is a red one in the switch, but now sure where the other probe should go.

    Click image for larger version. 

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    PS: I appreciate your comments. Maybe I'll end up having to take it to a pro, but so far I'm having fun with the process and trying it myself. I hope you are not getting bored with these newbie questions.

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    Don't forget the joker g1's Avatar
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    Quote Originally Posted by josegrad View Post
    One thing I've done every time I've switched it on is checking the bias capacitor, to see if there was any voltage stored in it. I haven't been able to get any readings from it so far. That cap is among the ones I have replaced.
    The voltage should be at the negative (-) end of that cap, and should be a negative DC reading.

    I'm sure I can do it safely but didn't measure that. I'm not sure where to place the probes. You mean just before the second switch? I know one of the cables is a red one in the switch, but now sure where the other probe should go.
    Black probe to ground, red probe to standby switch. First try one side of switch, if nothing check the other side. Should be +400VDC or more.

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    "When the amp was with all the valves on it didn't light up at first. With a wooden stick I hit here and there around the area where the diodes and bias cap are, and then it lighted up, not full light but clearly visible on. Sometimes it would go off and then on after hitting again.

    I took the valves out again and the bulb in the amp lights up normally, I can hit around with the stick and it just stays on.

    At least I guess I should take that part out and re-solder it again."


    That sure soumds like a bad connection to me...

    Justin

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    Here's the voltage at the second switch.
    No valves btw.

    Without hands...

    Click image for larger version. 

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    The reading:

    Click image for larger version. 

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    Last edited by josegrad; 11-03-2018 at 10:01 PM.

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    Quote Originally Posted by Justin Thomas View Post
    "That sure sounds like a bad connection to me...Justin
    Agree, I will re-solder that part of the amp.

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